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            <h2 class="title"><a id="dbexception"></a>Chapter 6. The DbException Class</h2>
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      <pre class="programlisting">#include &lt;db_cxx.h&gt;
class DbException {
public:
    int get_errno() const;
    virtual const char *what() const;
    DbEnv *get_env() const;
}; </pre>
      <p>
            This information describes the <code class="classname">DbException</code> class and how 
            it is used by the various Berkeley DB classes.
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      <p>
            Most methods in the Berkeley DB classes return an <code class="literal">int</code>, but also throw
            an exception. This allows for two different error behaviors. By default, the Berkeley DB
            C++ API is configured to throw an exception whenever a serious error occurs. This
            generally allows for cleaner logic for transaction processing because a try block can
            surround a single transaction. Alternatively, Berkeley DB can be configured to not throw
            exceptions, and instead have the individual function return an error code, by setting
            the <a class="link" href="envcreate.html#env_DB_CXX_NO_EXCEPTIONS">DB_CXX_NO_EXCEPTIONS</a>
            for the <a class="xref" href="dbcreate.html" title="Db">Db</a> and 
            <a class="xref" href="envcreate.html" title="DbEnv">DbEnv</a> constructors.
    </p>
      <p>
            A <code class="classname">DbException</code> object contains an informational string, an
            <code class="literal">errno</code>, and a reference to the environment from which the exception
            was thrown. The <code class="literal">errno</code> can be obtained by using the
            <code class="methodname">DbException::get_errno()</code> method, and can be used, in standard
            cases, to determine the type of the exception. The informational string can be obtained
            by using the <code class="methodname">DbException::what()</code>. And, the environment can be
            obtained using the <code class="methodname">DbException::get_env()</code> method.
    </p>
      <p>
            Where available, this class inherits from the standard class exception.
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      <p>
            Some methods may return non-zero values without issuing an exception. This occurs in
            situations that are not normally considered an error, but when some informational status
            is returned. For example, the <a class="xref" href="dbget.html" title="Db::get()">Db::get()</a> method returns
            <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
            when a requested key does not appear in the database.
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                <th>DB C++ Exceptions</th>
                <th>Description</th>
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                <td>
                  <a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a>
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                <td>Exception class for deadlocks</td>
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                <td>
                  <a class="xref" href="dblocknotgranted.html" title="DbLockNotGrantedException">DbLockNotGrantedException</a>
                </td>
                <td>Exception class for lock request failures</td>
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                <td>
                  <a class="xref" href="dbmemory.html" title="DbMemoryException">DbMemoryException</a>
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                <td>Exception class for insufficient memory</td>
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                <td>
                  <a class="xref" href="dbrephandledead.html" title="DbRepHandleDeadException">DbRepHandleDeadException</a>
                </td>
                <td>Exception class for database and cursor handles that are invalidated in a replicated application. </td>
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                <td>
                  <a class="xref" href="dbrunrecovery.html" title="DbRunRecoveryException">DbRunRecoveryException</a>
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                <td>Exception class for failures requiring recovery</td>
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